Conventionally, a solid state image sensor, such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS) image sensor, for example, is used in electronic equipment provided with an imaging function, such as a digital still camera or a digital video camera. The solid state image sensor has pixels in which photodiodes that perform photoelectric conversion and a plurality of transistors have been combined, and an image is constructed on the basis of pixel signals output from a plurality of pixels arranged on an image plane on which an image of a subject is produced.
Moreover, in recent years, in order to achieve size reduction and high performance of the solid state image sensor, a laminated-type solid state image sensor has been developed in which, on a sensor substrate on which pixels are formed, a signal processing substrate that performs signal processing on an image signal output from the sensor substrate has been laminated. In such a laminated-type solid state image sensor, composite bonding, such as physically connecting bonding surfaces of wafers and electrically connecting connection pads formed on the bonding surfaces is performed.
For example, Patent Literature 1 discloses a semiconductor device in which, by forming metal films entirely on bonding surfaces of two semiconductor substrates and performing a heating treatment in a state where the metal films are in contact with each other, portions of the metal films in contact with an interlayer insulation layer react to form an insulation film.